Means for suppressing ground currents



July 14,1931. G. MEYER 1,814,006

MEANS FOR SUPPRESSING GROUND CURRENTS Filed June 28, 1929 I N V E NTORGe rim/"2 Me yer.

'ar /im/y ATTORNEY Patented July 14, 1931 UNITED STATES PATENT OFFICEGERHART MEYER, OF BERLIN-CHARLOTTENBURG, GERMANY, ASSIGNOR TO WEST-INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL-VANIA MEANS FOR SUPPRESSING GROUND CURRENTS Application filed June 28,1929, Serial No. 374,349, and in Germany July 3, 1928.

My invention relates to improvements in means for suppressing groundcurrents, and more particularly for compensating completely the activeresidual ground current.

5 If an accidental ground develops the ground capacity of the soundconductor is according to my invention under-compeir sated to the sameextent as that of the other sound conductor is overcompensated. Theamount of this under-compensation or overcompensation respectivelydepends on the value of the active or line charging residual groundcurrent to be suppressed.

In the drawings affixed hereto and form- 1 ing part of my specificationFig. 1 shows a vector diagram of my improved ground suppressing device,

Fig. 2, a connection diagram of one embodiment of my invention, and

Fig. 3, a connection diagram of another embodiment of my invention.

I will now describe my invention with reference to Fig. 1 of thedrawings. U and U are the voltage vectors of the sound conductors incase of an accidental ground to ground, the value of which is equal tothe voltage from each of the sound phases to ground, as well known inthe art, and the phase displacement between which amounts to 60. Underthe action of the voltage U, a capacitive current flows across the pointwhere the accidental ground has developed which leads by 90 in respectto the voltage U and is indicated in the diagram by the reference J Inthe same way a capacitive current J as flows under the action of thevoltage U across the point where the accidental ground has developed.There also flows under the action of the voltage U an active current Jand under the action of the voltage U an active current J According tomy invention these four currents are compensated by an inductive currentJ by a certain amount smaller than the corresponding capacitive currentJ and an inductive current J larger by this amount than thecorresponding capacitive current JCS. The capacitive currents J and L,are consequently not completely compensated by these inductive currents,but the residual components (J J and (J J remain behind the value ofwhich must be so chosen that they neutralize the active residual groundcurrent (J J Preferably the inductance (Petersen coil, regulating chokecoil) common to all the phases is according to my invention chosenslightly smaller than would be necessary for the complete compensationof the capacitive residual ground current and in the event of a ground asecond inductance is then connected to only one of the sound or imactphases, whereby is obtained the desired compensation of the activeresidual ground current. When using a ground suppressing transformer thesecond inductance is prefer-ably connected to one of the two soundsecondary phase voltages of this ground transformer. The switching in ofthe scc- 0nd inductance is in both (2 ses preferably made dependent onan un: "oltage relay which is fed from the phase in which the accidentalground has developed. In view of the large voltages which must beutilized, it is obvious that the combination of circuit breakers andrelays would ordinarily be used. Since the second indr taucc is to bedimensioned only for the algebraic diifference of the currents (d J itbecomes considerably smaller than the cont non inductance. Furthermore,in tl e event of an accidental ground the algebraic diffcrence of thecurrents (J tic-J .11 only need be changed over, so that the rupturingcapacity for ,the switches of the second in ductance is far smaller thanif a change over of the full inductive ground current would have to beeffected.

Referring to Fig. 2 of the drawings, 4 is I 83 of the respective relays6, 7 and 8. Its

' tacts 63, 73

a transformer or generator from which issue the lines 1, 2, 3 of a hightension system.

The neutral point of this generator or trans-.

ground. One terminal of the energizing winding 61 of relay 6 isconnected to the line 1. winding 71 of relay One terminal of theenergizing winding 81 of relay 8 is connected to line The otherterminals of the respective energizing windings 61, 71 and 81, areconnected to ground.

The relays 6, 7 and 8 are normally energized to complete a circuitacross con- Ono terminal of the energizing of contact members 66, 76 and86, respectively. In their deenergized conditions the relays 6, 7 and 8complete a circuit across contacts 62, 72 and 82, respectively, by meansof contact members 64, 74B and 8%, respectively.

One of the contacts 62, of relay 6, is connected to line 30f the hightension system and the other contact 62 is connected to one of thecontacts 73 of relay 7. One of the contacts 72, of relay 7, is connectedto line 1 of the high tension system and the other contact 72 isconnected to one of the contacts 83 of relay 8. In a similar manner, oneof the contacts 82, ofxrelay 8, is connected to line 2 of the hightension system and the other contact 82 is connected to one of thecontacts 63 of relay 6. 9 is a second inductance, one terminal of whichis con nected to ground and the other terminal connected to the remamingcontacts 63, 73 and value for the case stated as example is 33.5 henry.V

The mode of operation of my improved system is as follows:

In the sound or intact state of the lines 1, 2, 3 the relays are in theposition shown in the drawings. If an accidental ground develops in oneof the lines, for instance in the line 3 the relay 8 is deenergized andconnects the line 2 through the contacts 82, contact member 84, contacts63, and contact member 66 to one terminal of the second inductance 9,and thence to ground, whereby the active residual ground current iscompensated, as fully described with reference to the diagram of Fig. 1of the drawings. For a ground on either lines 1 or 2, the correspondingrelays 6 or 7 would also be actuated to insert the inductance 9'in thecircuit. In Fig. 3 of the drawings lines 11, 12, 13 of a high tensionsystem are shown to which 7 is connected to line 2.

and 83, respectively, by means ated relays are connected thestar-connected primary windings of the transformer 20. The neutral pointof the transformer is directly grounded. The secondary windings of thetransformer are delta connected through variable inductance 50, as shownin the drawings. The value of this inductance at a system voltage of 220kv., 50 cycles, at a The relays 60, 70 and 80 are normally energizedtomaintain their respective contacts 162-163, 172173,and 182183 openand nocircuit is completed unless a fault occurs on the high tension system.One of the contacts 162 and 163 of'the relay 60 is'connected to thesecondary winding of 13. One of the contacts 172 and 173 of the relay 70is connected to the secondarywinding of the transformer correspondingwith the line 11. One of the contacts 182 and 183 of the relay 80 isconnected to the secondary winding of the transformer 20 correspondingwith the line 12. One terminal of a second inductance 90 is connectedtothe remaining contacts 162, 172 and 182 of the respective relays 60,70 and 80 and the other terminal thereof is connected to the. remainingcontacts 163, 173 and 183 of the respective relays 60, 70 and 80; Theirvalue for the case stated by way of example is 0.0098 henry.

This system functions in the following manner: In the sound or intactstate of the network the relays are in the switching position shown inthe illustration. If an-accis dental ground develops in the line 13, forinstance, the relay 80 connected in thisline is deenergized and connectsthrough the contacts 182, 183 and contact members 184, 186 respectively,the second inductance 90 parallel to the secondary winding of thetransformer corresponding with the line 12, whereby the active residualground current is again compensated. In the event of a ground on eitherline 11 or 12', the associ- 60 or 70 would be deenergiz'ed to close itsrespective contacts 162-163 or 17 2-173 by means of the respectivecontact iii-embers 164, 166 and 174:, 176, respectively,

the transformer 20 corresponding with the line be made without departingfrom the spirit and the scope oi the invention, and I desire, therefore,that only such limitations shall be placed thereon as are imposed by theprior art.

I claim as my invention:

1. In a high tension system, an inductance connected between the neutralpoint of said system and ground and so dimensioned that in case ofaccidental grounding of one line the ground capacities ofthe sound linesare undercompensated, a second inductance, and means adapted to connectsaid second inductance between a sound line and ground, said secondinductance so dimensioned, that the ground capacity of the sound line towhich said second inductance is connected is over-compensated to thesame extent as the other sound line is uncercompensated, the value ofthe undercompensation or overcompensation being so chosen that thecurrent resulting from the capacitive and inductive ground currents isequal and opposite to the line charging residual ground current.

2. In a high tension system, an inductance connected between the neutralpoint of said system and ground and so dimensioned that in case ofaccidental grounding of one line the ground capacities of the soundlines are under-compensated, a second inductance, a plurality of relays,electrically associated with said high tension system and ground andadapted in case of an accidental ground in one line to connect saidsecond inductance between a sound line and ground, said secondinductance so dimensioned that the ground capacity of the sound line towhich said second inductance is connected is overcompensated to the sameextent as the other sound line is undercompensated, the value of theunder-compensation or overcompensation being so chosen that the currentre sulting from the capacitive and inductive ground currents is equaland opposite to the line charging residual ground current.

3. In a high tension system, a transformer having its star-connectedprimary winding connected to the system and the neutral point of saidwinding connected directly to ground, and an inductance of suitablevalue connected to its secondary winding in order to load it in such amanner that in case of an accidental ground the ground capacities of thesound lines are undercompensated, the inductance opposing the groundcurrent being considerably smaller than the inductance of the system, asecond inductance, means for connecting said second inductance in caseof a ground to a secondary winding of said transformer correspondingwith one of the sound lines, said second inductance being so dimensionedthat the ground capacity of the sound line to the correspondingsecondary winding of the transformer to which the said second.inductanceis connected, is overcompensated to the same extent as the other soundline is undercompensated, the value of the undercompensation or overcoinivensation respectively being so chosen, that the current resulting fromthe capacitive and inductive ground currents is equal and opposite tothe line charging residual ground current.

4. In a high tension system, a transformer having its star-connectedprimary winding connected to the system and the neutral point of saidwinding connected directly to ground, and having its secondary windingconnected in delta and an inductance of suitable value connected to saidsecondary winding to electrically load it to such an extent that in caseof accidental grounding of the system the sound lines areundercompensated, and characterized in that the inductance actingcounter to the accidental ground current is considerably smaller thanthe working inductance of the system, a second inductance, a pluralityof relays electrically associated with said high tension:

system and ground and adapted in case of an accidental ground on oneline to connect said second inductance to a s condary winding of saidtransformer corresponding with a sound line, said second inductancebeing so dimensioned that the ground capacity of the sound line to thecorresponding secondary winding of the transformer to which the saidsecond inductance is connected, is overcompensated to the same extent asthe other." i

sound is undercompensated, and the value of the undercompcnsation orovercompensation respectively being so chosen, that the currentresulting from the capacitive and inductive ground currents equal andopposite to the line charging residual ground current.

5. In a high tension system, a transformer having its star-connectedprimary winding connected to the system and the neutral:

point of said winding connected directly to ground, and having itssecondary winding connected in delta and an adjustable induc tance ofsuitable value connected with said secondary winding to adapt saidtrain-:- former to the variable conditions of the high tension system insuch a way that in case of an accidental ground of one line the groundcapacities of the sound lines undercompensated, and characteri ed inthat the inductance acting counter to the ground current is considerablysmaller than the working inductance, a second inductance, means forconnecting said second inductance in case of accidental ground to asecondary winding of said transformer corresponding with a sound line,said second inductancebeing so dimensioned that the ground capacity ofthe sound line to the corresponding sec ondary winding of thetransformer to which ieu the said second inductance is connected isovercompensated to the same extent as the other sound lineis'undercompensated, and the value of the undercompensation orovercompensation respectively being so chosen, that the currentresulting from the capacitive and inductive ground currents is equal andopposite to the line charging residual ground current.

6. In a high tension system, a transformer having its star-connectedprimary winding connected to the system and the neutral point of saidwinding connected directly to ground, and having its secondary windingconnected in delta and an adjustable inductance of suitable valueconnected with said secondary winding to adapt said transformer to thevariable conditions of the high tension system in such a Way that incase of an accidental ground of one line the ground capacities of thesound lines are undercompensated, and characterized in that theinductance acting counter to the ground current is considerably smallerthan the Working inductance, a second inductance, a plurality of relayselectrically associated with said high tension system and ground, andadapted in case of an accidental ground on a line to connect said secondinductance to a secondary winding of said transformer corresponding withone of the sound lines, said second inductance being so dimensioned thatthe ground capacity of the sound line to the corresponding secondaryWinding of the transformer to which the said second inductance isconnected is overcompensated to the same extent as the'other sound lineis undercompensated, the value of the undercompensation or theovercompensation respectively being so chosen, that the currentresulting from the capacitive and inductive ground currents is equal andopposite to the line charging residual ground current.

7 In a polyphase electrical system, means for suppressing the groundcurrents occurring in the event of a phase-to-ground fault, includingrelay means electrically associated with said polyphase electricalsystem, inductance means associated with said system and said relays,means electrically associated With said system for undercompensating thecapacitive current of one of the non-faulty phases of said system andmeans for inserting said inductance means in circuit with said systemonly upon the actuation of one of said relay means to overcompensate thecapacitive current of another of said nonfaulty phases.

8. In a three phase system having undervoltage relay means electricallyassociated therewith, means for suppressing the ground currentsoccurring in the said system on the occurrence of a phase-to-groundfault ineluding means electrically associated with said system forundercompensating the caelectrically associated with said system onlyupon the occurrence of a phase-to-ground fault and the actuation of oneof said relay means.

In testimony whereof, I have hereunto,

subscribed my name this 17th day of June, 1929, at Berlin-Siemensstadt,Germany.

GERHART MEYER,

